The present invention relates to a clock and more particularly to a multi-year clock which is provided with a mechanism for automatically resetting the clock at the beginning and end of each daylight saving time period.
In places such as schools, factories, commercial buildings and the like where there are a large number of clocks that must all be reset at the beginning and end of each period of daylight saving time, it is desirable to be able to dispense with the troublesome reliance on human intervention to reset such clocks at the beginning and end of each such period. The resorting in the prior art to humans for taking care of the necessary time adjustments is both expensive and unreliable. This is true regardless of how simple the resetting procedure is rendered.
This is so because the seasonal daylight saving time adjustments are carried out during the middle of the night, usually around 2 A.M., when people are less alert. Further, where numerous clocks are dispersed throughout a large building and more than one individual is responsible for effecting the clock adjustments, a clock may be inadvertently reset twice. There is also the element of inconvenience involved because clocks are typically mounted high up on a wall where they can not be easily reached.
Master/slave clock systems are known in which several slave clocks are connected to a master clock and the seasonable clock adjustments are carried out at the master clock. The slave clocks respond automatically to the adjusting of the master clock. Such clock systems still suffer from the drawbacks that human intervention and actuation is required at the master clock and that slave clocks must be interwired with a master clock.
Recently introduced clocks can be programmed at the beginning of a year to automatically reset themselves during the transitions between standard and daylight saving time. These clocks respond to information which the user enters through a keyboard, dial or the like. However, even with these more sophisticated clocks, the clock user's intervention is still necessary, at least on a yearly basis. The long felt need for a stand-alone, master-less clock which will run uninterruptedly for years, even decades, and automatically adjust itself for daylight saving time, has not, to date, been satisfied by the prior art. Nor has the prior art satisfied the need for a master-less clock which is factory preprogrammed and simpler on account of the fact that it is not complicated by user controllable data entry devices such as keyboards, dials or the like.
The inventors herein are presently aware of certain patents relating to the subject matter of clocks/calendars, as follows. U.S. Pat. No. 3,277,645 to Hanson discloses a system for setting and maintaining a master clock 11 which is part of a master-slave clock system. Hanson's master clock has a so-called secondary drive mechanism, comprising a clock spring or a secondary synchronous motor which can be powered from a backup battery. The secondary drive mechanism serves to drive the movement of the master clock at its regular velocity even in the event of a power failure. Means are provided for advancing the clock one hour to set it from daylight saving time to standard time. Hanson's clock requires manual actuation for initiating daylight adjustments and does not have a memory.
U.S. Pat. No. 3,811,265 to Cater discloses a conventional, AC driven, clock 11 having an AC power source interruption detector 17. The AC interruption detector 17 serves to energize circuitry within the clock 11 from a battery for the duration of the AC power interruption.
U.S. Pat. No. 3,897,700 to Haydon discloses an apparatus for facilitating setting of a clock one hour ahead at the beginning of daylight saving time and back by one hour at the conclusion thereof. The time adjustments are initiated by maintenance personnel at each change of season.
U.S. Pat. No. 4,695,168 to Meister et al. discloses a clock which retains the correct date during power outages, even during replacements of a backup battery. Meister et al.'s clock has two motors and means for perpetually indicating the correct date which includes a date counter 31, a month counter 32 and a year counter 33. The counters provide signals to a correction circuit 34 so that the calendar automatically compensates for the length of each month and leap years. A nonvolatile memory 41 retains the contents of day, month and year counters during occasional power failures to assure restoration of the correct date when the power returns.
Other patents relating to the subject matter of the present invention include U.S. Pat. Nos. 4,447,160; 4,419,017; 4,271,494; 3,918,250; and 3,897,700.